Fused heater circuit with voltage reducing diode

ABSTRACT

A heated fill tube, for an icemaker, including a fluid tube and a heater circuit connected to the fluid tube. The heater circuit includes a heater element, a fuse in a series connection with the heater element and a diode also in series connection with both the fuse and the heater element. The diode includes an RMS voltage reducing diode and provides a reduced voltage to the heater element. The fuse includes an increased current rating corresponding to the reduced voltage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heated fill tube for an icemaker, and, more particularly, to a heater circuit used with the heated fill tube.

2. Description of the Related Art

Icemakers are known which automatically make ice. The icemaker can be part of an appliance such as a household refrigerator or can be a stand alone icemaker such as is used by a restaurant, for example. Icemakers are generally part of a refrigerated compartment that is maintained at a temperature below the freezing point of water. Icemakers typically include at least one fill tube, where each fill tube is connected to a source of water. The fill tube discharges the water into a plurality of cavities. When the water in the cavities is frozen an ejection device ejects the ice from the cavities into a container which holds the ice in a frozen state until the ice is used.

As the fill tube or tubes are also in the refrigerated compartment, that is maintained at a temperature below the freezing point of water, a heating device can be associated with each fill tube in order to keep the fill tubes from freezing the water in the fill tube as the water discharges into the cavities. The heating device keeps the fill tube from becoming obstructed with ice which thereby allows the fill tube to continue to fill the cavities with water as required by ice usage.

Heating devices are known that include a resistive heater with a source of voltage applied to the resistive heater. A fuse can be in series with the resistive heater to limit current in the event of an electrical short circuit. A fill tube heating device in a refrigerated compartment is somewhat contradictory in that the heating device creates an additional thermal load on the icemaker and can therefore reduce the efficiency of the icemaker. The fill tube heating device is required to output only the amount of heat per unit time necessary to keep the fill tube clear of ice. This low power output requirement for the heating device necessitates a low electrical current in the heating device as the power dissipated by the heating device is equal to the square of the electrical current in the heating device multiplied by the resistance of the heating device. This relationship in equation form is P=I²R=E²/R where P is the power dissipated by the heating device, I is electrical current in the heating device, R is the resistance of the heating device and E is the voltage applied across the heating device.

The above relationship holds for direct electrical current and voltage, or for alternating (AC) electrical current and voltage when the alternating electrical current and voltage are expressed in effective or equivalent values. Root-mean-square (RMS) refers to a common mathematical method of defining the effective voltage or current of an AC wave. In a circuit whose impedance consists of a pure resistance, the RMS value of an AC wave is often called the effective value or DC equivalent value. For example, if an AC source of 115 volts RMS is connected across a resistor, and the resulting current causes 50 watts of power to be dissipated by the resistor, then 50 watts of heat will also be dissipated if a 115 volt DC source is connected to the resistor.

Root-mean-square refers to a mathematical algorithm for the calculation of the effective value. The mathematical algorithm is the square root of the average of the square of the function for which you are calculating the RMS value. The RMS value for a time varying periodic function such as a sinusoidal wave, which is the function type for typical single phase utility power, is calculated by integrating the square of the periodic function over a single time period, dividing by the time period thus giving the average, and then taking the square root of the average. For a sinusoidal wave, the RMS value is 0.707 times the peak value. Utility voltages are expressed in RMS terms. A so-called “115 volt” AC circuit carries about 162.6 volts peak, or about 325 volts peak-to-peak.

A disadvantage of a low electrical current in the fill tube heating device is that a correspondingly small fuse is required for the heating device. Current limiting fuses can be can be given a current interrupting rating, for example, in RMS amperes. Fuses with fractional amperage ratings can be more expensive the smaller the amperage rating. For example, a 1/16 ampere (A) fuse can cost approximately $0.50 whereas a 1/32 A fuse can cost approximately $1.50 and a 1/64 A fuse can cost approximately $2.50.

What is needed in the art is a method and apparatus for increasing the fuse size in a fill tube heating device without increasing the power output of the fill tube heating device.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for increasing the fuse size in a heated fill tube without increasing the power output of the heated fill tube.

The invention comprises, in one form thereof, a heated fill tube for an icemaker, including a fluid tube and a heater circuit connected to the fluid tube. The heater circuit includes a heater element, a fuse in a series connection with the heater element and a diode also in series connection with both the fuse and the heater element. The diode includes an RMS voltage reducing diode and provides a reduced voltage to the heater element. The fuse includes an increased current rating corresponding to the reduced voltage.

An advantage of the present invention is the fuse size is increased for the heated fill tube.

Another advantage of the present invention is the power output of the heated fill tube is maintained.

Yet another advantage is of the present invention is the fuse cost is reduced for the heated fill tube.

A further advantage of the present invention is that it is easily implemented in the heated fill tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a sectional view of an icemaker with an embodiment of a heated fill tube of the present invention;

FIG. 2 is a schematic view of a prior art heating device;

FIG. 3 is a schematic view of an embodiment of heater circuit of the present invention; and

FIG. 4 is a schematic view of another embodiment of heater circuit of the present invention.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there is shown a heated fill tube 10, for an icemaker 12, which generally includes a fluid tube 14 and a heater circuit 16 connected to fluid tube 14.

Icemaker 12 includes wall 18 to which heated fill tube 10 is attached with fasteners 20. Icemaker 12 further includes at least one cavity 22 for forming ice.

Fluid tube 14 includes flange 24 which allows fluid tube 14 to be connected to icemaker 12 with fasteners 20. Inlet 26 is connected to a source of water (not shown) and this water can be discharged through channel 28 (hidden lines) into cavities 22.

Heater circuit 16 includes a heater element 30, a fuse 32 in a series connection with heater element 30 and a diode 34 also in series connection with both fuse 32 and heater element 30. Leads 35 allow heater circuit 16 connection to a source of alternating voltage. Diode 34 comprises an RMS voltage reducing diode and provides a reduced voltage 36 to heater element 30. Fuse 32 includes an increased current rating {square root}2CR corresponding to reduced voltage 36.

Heater element 30 can be a metallic resistance wire wrapped around a fabric, for example. Heater element 30 can be spirally wrapped around and/or embedded within fluid tube 14 to provide an even heat distribution over fluid tube 14.

An alternating voltage 38 (FIG. 3) can be connected in series with heater element 30, diode 34 and fuse 32. Alternating voltage 38 can be an approximately 120 volts RMS sinusoidal waveform that is commonly available utility power. Diode 34 is a blocking or rectifying diode which blocks one half of each periodic wave of alternating voltage 38. Reduced voltage 36 therefore has a value of approximately 120/({square root}2) volts RMS=84.85 volts RMS.

In contrast, resistive heater 42 of prior art heating device 40 has the full approximately 120 volts RMS across resistive heater 42. For a resistance of 4.5 kΩ (kilo-ohm), for example, in resistive heater 42, the current in prior art heating device 40 is (120 volts RMS)/4.5 kΩ=0.0267 amperes RMS. The current rating CR in fuse 44 of prior art heating device 40 is therefore 1/32 amperes RMS. The power output of prior art heating device 40 is equal to (120² volts RMS)/4.5 kΩ=3.2 watts.

For an equivalent power output, heater element 30 of heater circuit 16 is required to have one half the resistance of resistive heater 42. Heater element 30 is therefore 2.25 kΩ, for example, to produce the same power output of resistive heater 42 described above since reduced voltage 36 is applied to heater element 30. The power output of heater element 30 is equal to (84.85² volts RMS)/2.25 kΩ=3.2 watts. However, the current in heater element 30 is (84.85 volts RMS)/2.25 kΩ=0.0377 amperes RMS. The increased current rating {square root}2CR in fuse 32 of heater circuit 16 is therefore 1/16 amperes RMS which thus allows for the aforementioned advantages.

While the embodiment of FIG. 3 shows heater element 30 connected to both fuse 32 and diode 34, in the embodiment of FIG. 4, heater circuit 46 has fuse 32 connected to both heater element 30 and diode 34. Alternatively, diode 34 can be connected to both heater element 30 and fuse 32.

While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims. 

1. A heated fill tube for an icemaker, comprising: a fluid tube; a heater circuit connected to said fluid tube, said heater circuit including a heater element, a fuse in a series connection with said heater element and a diode also in said series connection with both said fuse and said heater element, said diode comprising an RMS voltage reducing diode and providing a reduced voltage to said heater element, said fuse including an increased current rating corresponding to said reduced voltage.
 2. The heated fill tube of claim 1, further including an alternating voltage in said series connection with said heater element, said diode and said fuse.
 3. The heated fill tube of claim 1, wherein said diode is a rectifying diode.
 4. The heated fill tube of claim 1, wherein said heater element is wrapped around said fluid tube.
 5. The heated fill tube of claim 1, wherein said heater element is connected between said fuse and said diode.
 6. The heated fill tube of claim 1, wherein said fuse is connected between said heater element and said diode.
 7. A heater circuit, comprising: a heater element; a fuse in a series connection with said heater element; and a diode also in said series connection with both said fuse and said heater element, said diode comprising an RMS voltage reducing diode and providing a reduced voltage to said heater element, said fuse including an increased current rating corresponding to said reduced voltage.
 8. The heater circuit of claim 7, wherein said heater circuit is configured for connection to an alternating voltage.
 9. The heater circuit of claim 7, wherein said diode is a rectifying diode.
 10. The heater circuit of claim 7, wherein said heater element is connected between said fuse and said diode.
 11. The heater circuit of claim 7, wherein said fuse is connected between said heater element and said diode.
 12. A method of connecting a heater circuit; comprising the steps of: providing a source of alternating voltage; serially connecting a heater element and a fuse with said source of alternating voltage; connecting a diode to said source of alternating voltage and said heater element; reducing a voltage to said heater element; and increasing a current rating in said fuse.
 13. The method of claim 12, further including the step of wrapping said heater element around a fluid tube. 